WHOLLY AROMATIC THERMOTROPIC LIQUID-CRYSTALLINE POLYESTERS OF 3,3'-BIS(PHENYL)-4,4'-BIPHENOL WITH 4,4'-BENZOPHENONE DICARBOXYLIC-ACID

A series of wholly aromatic, thermotropic polyesters, derived from 3,3 '-bis (phenyl)-4,4'-biphenol (DPBP), nonlinear 4,4'-benzophenone dicar boxylic acid (4,4'-BDA), and various linear comonomers, were prepared by the melt polycondensation reaction and characterized for their ther motropic properties by a variety of experimental techniques. The homop olymer of DPBP with 4,4'-BDA had a fusion temperature (T-f) at 265 deg rees C, exhibited a nematic phase, and had a liquid crystalline range of 105 degrees C. All of the copolyesters of DPBP with 4,4'-BDA and ei ther 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), or 50 mol % terephthalic acid (TA), 2,6-naphthalenedicarboxylic acid (2,6-NDA) had low T-f values in the range of 220-285 degrees C, exhibited a nematic phase, and had accessible isotropization transitio ns (T-f) in the range of 270-420 degrees C, respectively. Their access ible T-i values would enable one to observe a biphase structure. Each of the copolymers with HBA or HNA had a much broader range of liquid c rystalline phase. In contrast, each of the copolymers with TA or 2,6-N DA had a relatively narrow range of liquid crystalline phase. Each of these polyesters had a glassy, nematic morphology that was confirmed w ith the DSC, PLM, WAXD, and SEM studies. As expected, they had higher glass transition temperatures (T-g) in the range of 161-217 degrees C than those of other liquid crystalline polyesters, and excellent therm al stabilities (T-d) in the range of 494-517 degrees C, respectively. Despite their noncrystallinity, they were not soluble in common organi c solvents with the exception that the homopolymer and its copolymer w ith TA had limited solubility in CHCl3. However, they were soluble in the usual mixture of p-chlorophenol/1,1,2,2-tetrachloroethane (60/40 b y weight) with the exception of the copolymer with 2,6-NDA. (C) 1997 J ohn Wiley & Sons, Inc.